Self-centering bit



y 1957 s. E. VlCK 2,792,726

- SELF-CENTERING BIT Filed May 4, 1953 I. .1. V -z.

7 Q INVEN R ATTORNEYS United States Patent-O SELF-CENTERING BIT Selmer E. Vick, Lakeville, Minn. Application May 4, 1953, Serial No. 352,919

4 Claims. (Cl. 77-55) The present invention relates broadly to improvements in centering tools and more specifically to a self-centering bit having improved construction and simplicity as also highly improved operational characteristics.

it has been found diificult in prior self-centering tools to drill accurately in various materials and in special uses without additional tools such as chisels to bias the bit after an initial countersink has been bored. A power operated drill, for example, has a tendency to drill off-center due to centripetal action, for which reason the biasing is necessary to offset this tendency.

Additionally, previous attempts to provide a self-centering bit or tool .have resulted in complicated and expensive mechanisms which failed to satisfy the desired results.

It is an object of the present invention to provide a selfcentering bit which overcomes the drawbacks of previous known devices of a similar nature and which satisfies all requirements for a tool of this nature.

It is also an object of this invention to provide a selfcentering bit which is of simple and sturdy construction and which is also highly efficient in operation.

Further objects and advantages of the present invention will be apparent from the following detailed description of an embodiment of the invention taken together with the accompanying drawings in which:

Figure 1 is a side elevational view of the self-centering bit of the present invention;

Fig. 2 is a sectional view of the device of Fig. 1, showing the bit in operation;

Fig. 3 is a cross-sectional view taken on line 3-3 of Fig. 1; and

Fig. 4 is a cross-sectional view taken on line 44 of Fig. 1.

The self-centering bit of the present invention, as shown in the drawings, consists in an outer barrel having a plug 11 secured in one end. The barrel 10 and plug 11 have mating screw threaded bores 12 therein. An Allen screw 13 is inserted in the bores 12 for a purpose hereinafter to be set forth.

The plug 11 also has a longitudinal bore 14 opening into the interior of barrel 10. An inner sleeve 15 is slidably inserted in barrel 10 as shown in detail in Fig. 2. The inner sleeve 15 is slotted or grooved at 16 so as to provide a fiat surface.

Barrel 10 has a peripheral slit 17 through a side thereof int which a retainer pin 18 is inserted. The retainer pin 18 is driven into the side of barrel 10 through slit 17 and cooperates with shoulder 19 on inner sleeve 15 to limit the movement of the same within barrel 10.

A spring 20 acting between the end 21 of inner sleeve 15 and plug 11 biases sleeve 15 to an extended position with respect to barrel 10 as limited by retainer pin 18 cooperating with shoulder 19.

Inner sleeve 15 also has a longitudinal bore 22 therethrough which in conjunction with bore 14 permits insertion of a bit 23 through the tool.

The outer end 24 of inner sleeve 15 is beveled at 25 so "ice that it will fit the countersink of cabinet hinges 26 or any similar constructions to facilitate centering of the tool. The Allen screw 13 serves to secure bit 23 in the bores 14 and 22 in a fixed position. The inner sleeve 15 slides with respect to bit 23.

Both the barrel 10 and inner sleeve 15 are provided with a plurality of radial holes 27 which permit the escape of any shavings which may follow or flow up the bit 23 into either the sleeve 15 or barrel 10.

The self-centering bit of the present invention is usable in either electric or hand operated drills since the bit 23 is secured in the same manner in either one.

When placed against a hole in any hinge plate, for example, the sleeve 15, through level 25, automatically centers the bit and upon pressure from the operator, the sleeve 15 slides into the barrel and the bit 23 will bore into the material and is maintained centered during the entire drilling operation.

Because of the limits of movement of the sleeve 15, the depth of drilling is accurately controlled. The actual depth of drill-ing can be adjusted by means of adjusting the position of Allen screw 13 with respect to bit 23.

In operation, the bit 23, inner sleeve 15, and barrel 10, all revolve as a single unit. The only relative movement between the parts occurs as the inner sleeve. slides back and forth between the bit and the barrel.

Manifestly minor changes in details of construction will be apparent to those skilled in the art to which the present invention pertains without departing from the spirit and scope of the present invention as defined in the appended claims.

I claim:

1. A self-centering bit comprising an outer barrel member having a peripheral transverse slit formed therein, an inner sleeve member slidably positioned in the forward end of said outer barrel member, a bit secured to said outer member and slidably contained in said inner sleeve member, means carried by said barrel biasing said inner sleeve forwardly and outwardly of said outer barrel member, said inner sleeve having a longitudinally extending flattened portion terminating in longitudinally spaced transverse abutments, and a retaining pin secured in said slit against movement and co-acting with said abutments and with said flattened portion of said inner sleeve to limit the longitudinal movement of said inner sleeve with respect to said outer barrel and cause said inner sleeve to rotate with said outer barrel.

2. A self-centering bit as claimed in claim 1, a plug secured in the upper end of said outer barrel remote from the inner end of said inner sleeve and through which said bit extends, said biasing means comprising a spring interposed between said plug and inner end of said inner sleeve.

3. A self-centering bit as defined in claim 2, a threaded bore through said barrel and said plug, adjustable screw means engageable in said bore engageable with said bit for securing said bit in a desired adjusted position.

4. In a self-centering bit, an outer barrel member having a peripheral transverse slit formed therein, an inner sleeve member slidably positioned in the forward end of said outer barrel member, said inner sleeve having a re cess formed therein terminating in longitudinally spaced transverse abutments, a pin secured in said slit against movement and coacting with said abutments and within said recess to limit longitudinal movement of said inner sleeve with respect to the forward end of said outer barrel and to cause said inner sleeve to rotate with said outer barrel, a bit secured to said outer member and slidably extending through said inner sleeve, spring means carried by said barrel and contacting the upper end of said 3 inner sleeve to bias said inner sleeve outwardlyof said 2,224,481) outer barrel member. 2,335,614 2,479,774 References Cited in the file of this patent UNITED STATES PATENTS 5 1,152,070 Borgeson Aug. 31, 1915 649862 1,596,197 Lindgren Aug. 17, 1926 4 Kartarik Dec. 10, 1940 Spievak Nov. 30, 1943 Pierce Aug. 23, 1949 FOREIGN PATENTS Great Britain Aug. 2, 1950 

